A nine year old spayed female greyhound was presented to the emergency and internal medicine services at the Cornell University Companion Animal Hospital (CUHA-CAH) for evaluation and treatment of chronic diarrhea. Bloodwork and abdominal radiographs obtained by the referring veterinarian failed to yield a diagnosis and a variety of symptomatic therapies had been implemented with little or no reduction in clinical signs. Endoscopic and colonoscopic examination of the gastrointestinal tract at CUHA-CAH revealed diffuse thickened, irregular, friable and hyperemic mucosa with evidence of necrosis and mucosal sloughing. Histopathologic examination of endoscopically obtained mucosal biopsies yielded a diagnosis of chronic severe diffuse lymphocytic-plasmacytic inflammatory bowel disease. The etiology, pathogenesis, diagnosis, and treatment of inflammatory bowel disease are reviewed within the context of this case report.